Improvement in derricks



Q. A 6% Q A. K. RICHMOND.

Derricks.

Patented Dec. 23,1873.

Fig.3.

UNITED STATES PATENT OFFICE.

ALBION K. RICHMOND, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN DERRICKS.

Specification forming part of Letters Patent No. 145,899, dated December 23, 1873; application filed December 10, 1873.

To all whom it may concern.-

Be it known that I, ALBION K. RICHMOND, of Boston, of the county of Suffolk and State of Massachusetts, have invented a new and useful Improvement in BoomDerricks; and do hereby declare the same to be fully described in the following specification and rep resented in the accompanying drawings, of which Figure 1 denotes a front elevation, Fig. 2 a side view, and Fig. 3 a longitudinal section, of the upper portion of a derrick-mast provided with my improvement.

In constructing ordinary derricks, it has been customary to arrange the sheave at the head of the mast, within a slot made directly through such head atits middle, in consequence of which the mast becomes much weakened, so as to be liable to break at or near such hole, and especially just below such, where it is essential to have the mast very strong.

In carrying out my invention, I arrange two sheaves on opposite sides of the mast, near its head, and support them in socketed caps fixed to the mast, and I extend the metallic pintle of the mast-head down into the mast and between the sheaves and below them, and into the neck of the mast some seven to ten feet, generally speaking.

In the drawings, A represents the upper portion of a derrick mast; B B, the two sheaves 5 O 0, their socketed caps, and D the metallic pintle that usually supports the crab from where the guy-ropes project. By Fig. 3 of the drawings, it will be seen how the pintle D extends below the sheaves and the neck, and into the body of the mast, it serving to protect the mast from breakage at the neck, and where the mast gives support to the sheaves.

Were a single sheave used in a slot formed through themiddle of themast, the pintle could not be extended down within the mast and below the sheave, to give strength to the neck of the mast, for the sheave would be an obstacle to prevent such extension.

By employing two sheaves on opposite sides of the mast, the boom-tackle can be run about both of them, whereby the strain of it on one side of the mast will be counterbalanced by that of the other side, and the mast be prevented from bending laterally, the pintle, by its extension, effectually serving to prevent breakage of the mast at its weakest part.

I claim- In a derrick, two sheaves, B B, arranged and supported on opposite sides of the mast A, in combination with the crab-pintle D, extended down between and below such sheaves, and into the neck or body of the mast, all substantially as described and represented.

ALBION K. RICHMOND.

Witnesses:

R. H. EDDY, S. N. PIPER. 

